In a new study, a third of the food wrapper samples collected from McDonald’s, Burger King, Starbucks and other restaurants contained fluorine, a marker for a controversial group of chemicals used to resist grease, oil and water in consumer products. (Zbigniew Bzdak / Chicago Tribune)

In a new study, a third of the food wrapper samples collected from McDonald’s, Burger King, Starbucks and other restaurants contained fluorine, a marker for a controversial group of chemicals used to resist grease, oil and water in consumer products. (Zbigniew Bzdak / Chicago Tribune)

For more than three decades, fast-food chains have relied on the chemical industry to keep grease and oil from soaking through burger wrappers, french fry cartons and pizza boxes.

Few questioned the safety of the specially coated food packaging until the early 2000s, when lawsuits uncovered the history of a class of chemicals that were widely used in consumer goods with practically no government oversight.

Researchers slowly began to realize that many of those compounds, known as perfluorinated chemicals, or PFCs, break down in people’s bodies to a chemical called PFOA that lingers in the bloodstream for years. Other studies determined that PFOA can cause cancer, damage the liver, trigger reproductive problems and scramble hormones during critical stages of development.

It turned out food wrappers were a major source of exposure. Under oath, a former DuPont chemist described how customers ingested the chemicals every time they ate a french fry.

McDonald’s, Burger King and other chains pledged to stop using the chemicals, and manufacturers began to phase them out. Last year, the Food and Drug Administration banned the use of three PFCs in food packaging.

But some fast-food restaurants continue to rely in part on grease-resistant packaging made with structurally similar chemicals that remain largely unknown to independent researchers, many of whom are concerned about potential health risks.

In a new study, a third of the samples collected from McDonald’s, Burger King, Starbucks and other restaurants contained fluorine, a key building block in PFCs. Some contained traces of PFOA, one of the chemicals banned by the FDA — though the study does not identify which chains sold packaging with the substance.

The study, published Wednesday in the peer-reviewed journal Environmental Science & Technology Letters, highlights the long, often difficult process of identifying new chemicals in the marketplace and determining if they can cause harm. It also raises questions about corporate branding. McDonald’s and Burger King, for instance, have promoted their packaging as “PFOA-free,” meaning it doesn’t contain banned PFCs.

Fluorine, however, was detected in samples collected from both chains — indicating companies have embraced chemicals related to PFOA.

“We just don’t know enough about the safety of these new chemicals,” said David Andrews, a senior scientist at the Environmental Working Group who co-authored the study with researchers from federal and state agencies, universities and other nonprofit organizations. “Since there are other options out there, this should be a wake-up call for these companies.”

Zbigniew Bzdak / Chicago Tribune

McDonald's grease-resistant food packaging is seen in Chicago on Feb. 1, 2017. In a new study, a third of the samples collected from McDonald’s, Burger King, Starbucks and other restaurants contained fluorine, a marker for a controversial group of chemicals used to resist grease, oil and water in consumer products.

McDonald's grease-resistant food packaging is seen in Chicago on Feb. 1, 2017. In a new study, a third of the samples collected from McDonald’s, Burger King, Starbucks and other restaurants contained fluorine, a marker for a controversial group of chemicals used to resist grease, oil and water in consumer products.

(Zbigniew Bzdak / Chicago Tribune)

PFOA and related chemicals were used for decades to make Teflon, the nonstick coating pioneered by DuPont, and thousands of other products that resist stains, grease and water. Manufacturers say their replacements, described as “short-chain” because they contain fewer fluorine-carbon bonds than PFOA, offer the same benefits but leave the body faster and are considerably less toxic.

“Any further regulation of modern-day short-chain food packaging materials is unnecessary and would provide no further benefits to human health or the environment,” the American Chemistry Council, the industry’s chief trade group, said in a statement.

When researchers attempted to find out if fast-food chains were aware of PFCs in their packaging, two unnamed companies said they believed their packaging was PFC-free even though it wasn’t, according to the study.

McDonald’s said in a statement that its packaging “does not contain PFAS,” another acronym for PFCs. But of the 31 McDonald’s wrappers tested by researchers, 19 percent contained fluorine, a marker of the chemicals.

“Our packaging is safe for intended use and contains materials that meet FDA standards,” the company said.

Many of the wrappers and cartons tested did not contain PFCs. The study’s authors suggested that could indicate restaurants obtain packaging from different suppliers, some of which use alternative methods to make paper grease-resistant. At least three manufacturers make food packaging that are free of PFCs, the Environmental Working Group found.

The presence of PFOA, the banned PFC, in some packaging could have come from recycled paper, researchers said.

Several environmental scientists pointed to a replacement chemical developed by DuPont as an example of a questionable alternative. In documents submitted to the Environmental Protection Agency between 2006 and 2013, DuPont reported the chemical, branded as GenX, caused some of the same health problems in laboratory rats that PFOA does, including cancer and reproductive problems. Company scientists downplayed the findings by saying they weren’t relevant to humans, echoing what DuPont had said earlier about PFOA.

“If we can all agree that PFOA is hazardous, but then we test its replacements with basically the same assays that gave it a ‘passing grade,’ aren’t we missing something?” said Laura Vandenberg, a researcher at the University of Massachusetts-Amherst who was not involved in the new study.

More research is needed on the potential hazards of short-chain PFCs at levels similar to how people might be exposed to the chemicals, Vandenberg and others said. But that work can take years, in part because the identities of many chemicals are considered trade secrets and manufacturers aren’t required to tell the FDA or EPA when they are used in food packaging or other products.

In 2015, a top federal scientist and more than 200 other researchers urged manufacturers to limit the use of all PFCs.

“Such straightforward replacement strategies may be cost effective in the short term,” Linda Birnbaum, director of the National Institute of Environmental Health Sciences, wrote in an editorial published by the journal Environmental Health Perspectives. “However, manufacturers may yet incur costs if the closely related alternative is later found to be as toxic as its predecessor.”

Though PFCs have been widely used for decades, little was known about the chemicals until lawyers began obtaining internal DuPont documents in the early 2000s as part of a lawsuit filed by neighbors of one of the company’s manufacturing plants along the Ohio River in West Virginia. A legal settlement required the company to finance a detailed study of thousands of people who were exposed to the chemicals in drinking water.

Federal juries in Ohio have since found DuPont liable for diseases caused by PFOA and ordered the company to pay three multimillion-dollar verdicts. The company, which spun its perfluroninated chemicals unit into another company called Chemours, faces at least 3,500 other lawsuits related to the chemical.